Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front elevation view of a display screen or portion thereof with transitional graphical user interface, showing a first image of our new design;

FIG. 2 is a second image thereof;

FIG. 3 is a third image thereof;

FIG. 4 is a fourth thereof;

FIG. 5 is a fifth thereof;

FIG. 6 is a sixth thereof;

FIG. 7 is a seventh image thereof;

FIG. 8 is an eighth image thereof; and,

FIG. 9 is a ninth image thereof.

The outer broken lines showing of the display screen or portion thereof are for the purpose of illustrating environmental structure and form no part of the claimed design. All other broken lines showing of the graphical user interface are for the purpose of illustrating environmental structure and form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-9. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 